...the mix of IFR and VFR traffic is potentially catastrophic.
...The current system is at fault and there are many potential solutions not least mandatory TCAS for all aircraft.
Why IFR/VFR? Why TCAS? There are plenty of places that manage the mix at much higher levels of traffic density. In this case it doesn't even appear anyone was IFR - it is a problem that could happen anywhere - other than an airport that allows only radar vectored ILSs.
Something clearly has gone badly wrong and as an industry we need to understand and respond. But even with TCAS and Mode S and IFR only operations and two person crews and positive radar control we have unfortunately demonstrated twice in recent years you can still crash aircraft into each other. Once the facts are available, then solutions can be proposed.